Halo 4 U.K. Launch

Halo 4 launched in the U.K. with an aerial lighting performance visible for miles over London. Several other events were held around the city to celebrate the launch of one of the year’s most anticipated video games.

According to an open letter signed by hundreds of scientists and technology experts, artificial intelligence could be used to build weapons with minds of their own. Here are five important things to know about artificial intelligence.